IMMUNOCYTOCHEMICAL LOCALIZATION OF STEROIDOGENIC ENZYMES IN GONADS DURING SEX DIFFERENTIATION IN TILAPIA

摘要

The phenotypic sex of many teleost fish can be experimentally altered by sex steroid hormones (Hunter and Donaldson, 1983: Yamazaki, 1983). Yamamoto (1969) hypothesized on the basis of the experimentally the administrations of various steroids that steroids are the natural inducers of gonadal sex differentiation in medaka Oryzias latipes. However, the role of endogenous steroid hormones on the gonadal sex differentiation in fish is still unknown. We reported in previous studies that steroid-producing cells appeared ultrastructurally at the same time as the initial ovarian and testicular differentiation in tilapia, (Nakamura and Nagahama, 1985 and 1989). In this study, were examined immunocytochemically the initial differenitation and developmentof steroid-producing cells during gonadal sex differentiation using policlonal antibodies against four steroid-metabolizing enzymes essential for biosynthesis of all major sex steroid hormones including androgens and estrogens: cholesterol side chain cleavage cytochrome P450 (P450scc), 3 beta-hydroxysteroid dehydrogenase (30-HSD), cytochrome 17 alpha-hydroxylase/17,20-lyase (P450cl7), and cytochrome P450 aromatase (P450arom).